I am about to add a new vinyl window to an existing exterior garage wall.
The inside of the garage wall is now just open studs, but I will be adding
insulation to the wall and then sheetrock.
The outside of the wall is aluminum siding on top of some type of 1/2 inch
siding (I don't know what it is called) that is nailed to the studs.
Cutting the opening for the window and framing it out with a header etc.
will not be a problem -- I know how to do that.
My question is about what to do on the outside. If I buy a new window, it
will have a flap/flange(?) around the outside that is for nailing the new
window to the studs. But, if I cut back the aluminum siding to allow for
the flaps to be nailed to the studs, how do I finish off the space between
the edge of the aluminum and the window itself?
Is there some other trick for doing this such as to cut off the flaps and
nail the window in place through the sides so the aluminum will meet the
edge of the window?
Either way will work. A real window supplier will be able to get 'old
work' windows without the nailer flange. You surround the opening with
J-channel to catch the cut ends of the siding before you pop the window
in the opening. Or if you cut back the siding, you trim around the
window with 1x4 or whatever, again with J-channel to catch the siding.
I'd key off whatever the other windows in the house look like. Usual
cautions about sealing membranes and shoving flashing up under the
siding above the window apply. Leaks around the outside are the main
failure point for a cut-in window. Absolute safest way is to strip
enough of the siding to install it just like a new construction window,
and then side back up to it. If you can pull the old siding off without
destroying it, it should go right back up with no problems. People
scorn at aluminum, but unless it was nailed too tight, it actually
reinstalls better than vinyl, which takes a set from the UV. If you
number the pieces and keep track, you can even keep the fade patterns
Thanks. I did the job today and it is working out okay. I did it by
cutting the flanges off. I didn't have any J-channel, but instead I used
the window frame itself to overlap and cover the aluminum siding. I still
have caulking left to do, but it started raining so I'll go back tomorrow to
finish the job.
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